Determination of buprenorphine in raw material and pharmaceutical products using ion-pair formation

A simple and sensitive extractive spectrophotometric method has been described for the determination of buprenorphine either in raw material or in pharmaceutical formulations. The developed method is based on the formation of a colored ion-pair complex (1 : 1 drug/dye) of buprenorphine and bromocresol green (BCG) in buffer pH 3 and extracting in chloroform. The extracted complex shows absorbance maxima at 415 nm. Beer's law is obeyed in the concentration range of 1.32-100.81 μg mL−1 . The proposed method has been applied successfully for the determination of drug in commercial sublingual tablets and injectable dosage form. No significant interference was observed from the excipients commonly used as pharmaceutical aids with the assay procedure

Synthesis of 6-(2-Methoxynaphthyl)-2,3-dihydro-1,2,4-triazine-3-thione as a New Reagent for Spectrophotometric Determination of Copper

A simple, sensitive, accurate, and green spectrophotometric method for the determination of Cu(II) using newly synthesized reagent, 6-(2-methoxynaphthyl)-2,3-dihydro-1,2,4-triazine-3-thione (MNDTT), has been developed. MNDTT was synthesized based on the acylation of methoxy naphthalene and reaction of the product with amyl nitrite, which upon reaction with thiosemicarbazide yielded 6-(2-meyhoxynaphthyl)-2,3-dihydro-1,2,4-triazine-3-thione. MNDTT produces a dark red complex with copper in methanol according to the 1 : 2 stoichiometry. Beer’s law was obeyed over the concentration range of 2.5–20 µg/mL with r2=0.992. The limit of detection and limit of quantification were 0.33 and 1.10 µg/mL, respectively. Within-day and between-day precision values were less than 3.68%. Finally, the method has been applied to a dental alloy (110-plus) successfully and the results were compared with atomic absorption method. The results showed that there was no significant difference between the two methods (P>0.05)

A Stability-Indicating HPLC Method for the Determination of Fingolimod in Pharmaceutical Dosage Forms

Fingolimod is an immunosuppressive agent which is used for the prophylaxis of organ transplantation rejection or multiple sclerosis treatment. In this study, systematic forced degradation studies on fingolimod bulk powder were performed to develop a stability-indicating HPLC method. Separation of fingolimod and its degradation products was achieved on a Nova-Pak C8 column. The mobile phase was a mixture of potassium dihydrogenphosphate 50 mM (pH 3.0) and acetonitrile (45:55, v/v) at a flow rate of 1 ml/min. The proposed method was linear in the range of 0.125–20 μg mL−1. The within-day and between-day coefficients of variation were in the range of 0.6–1.2%. The developed method was successfully applied for the determination of the fingolimod amount in pharmaceutical dosage forms

Stereospecific Determination of Mefloquine in Whole Blood by HPLC

Mefloquine, as a racemic mixture, is used for the treatment and prophylaxis of malaria. Stereoselective pharmacodynamic and pharmacokinetic differences has been observed for mefloquine. In this study a modified stereoselective HPLC method is presented for determination of mefloquine (MFQ) enantiomers in whole blood. The assay involved liquid-liquid extraction of MFQ from biological fluids with methyl tert-butyl ether in the presence of sodium hydroxide and derivatization of the residue by (+)-1-(9-fluorenyl) ethyl chloroformate (FLEC) as chiral derivatizing reagent. Separation of the resulting diastereomers was performed on a Novapack C18 reversed-phase cartridge column using acetonitrile, water, glacial acetic acid (730:270:0.7, v/v/v) as the mobile phase with a flow-rate of 1 mL/min. Using 500 μ L of whole blood, the limit of determination was 50 ng/mL with fluorescence detection with excitation at 263 nm and emission at 475 nm for both enantiomers. This method is comparatively simple and practical for the determination of small amounts of mefloquine enantiomers

An Ex-Vivo Study on the Stereoselective Accumulation of Mefloquine Enantiomers in Human Blood Fractions: Accumulation of mefloquine in blood

Mefloquine (MFQ), as a racemic mixture is used for the prophylaxis and treatment of malaria. Stereoselective pharmacodynamic and pharmacokinetic differences have been observed for MFQ. In the present study, the human blood was spiked with racemic MFQ. The concentration of MFQ enantiomers in various blood fractions including packed erythrocyte layer, platelet rich plasma and platelet poor plasma was determined. The results showed that the ratio of (+)-MFQ was about 1.5 time higher than (-)-MFQ in packed erythrocyte layer. Results obtained from the separated erythrocytes spiked with racemic MFQ showed no significantdifference between the enantiomer concentrations. It can be concluded that the stereoselective accumulation of MFQ enantiomers in erythrocytes might be in relation to protein binding or the presence of other blood cells

A High-Performance Liquid Chromatographic Assay for the Determination of Losartan in Plasma

A rapid and sensitive HPLC method was developed for determination of losartan in plasma. Losartan was extracted from plasma by a two-step extraction procedure using chloroform as extracting solvent in acidic medium. HPLC analysis was performed on a cyano reversed-phase column using phosphate buffer (pH 4.3), acetonitrile (750:250, v/v) as mobile phase with a flow rate of 0.9 mL/min. Sodium diclofenac was selected as internal standard. Excellent linearity between the peak area ratios and losartan concentrations over the range of 2-200 ng/mL of plasma was observed. The limit of determination with UV detection at 225 nm, with a CV < 5% was 2 ng/mL in 500 μL of plasma sample. The assay was rapid, safe and reliable for use in pharmacokinetic studies of losartan in human being

Spectrophotometric Determination of Tropicamide in Bulk and Pharmaceutical Formulations: Determination of tropicamide

Asimple and sensitive extractive spectrophotometric method is described fordetermination of tropicamide. The method is based on the reaction of tropicamideand bromocresol green. The ion-paired colored complex was extracted withchloroform at pH 3. The extracted complex showed maximum absorbance at 423nm. The complex was stable up to 2 days and obeyed Beer's law over theconcentration ranges of 1.32-100.81 μg/ml. No significant interference was observedfrom the excipients, coloring and flavoring agents commonly used in the tropicamidepharmaceutical preparations. The proposed method was applied successfully fordetermination of tropicamide in commercial eye drop dosage forms

Development and Validation of a Rapid Derivative Spectrophotometric Method for Determination of Tropicamide in Eye Drops: Determination of tropicamide in eye drops

Tropicamide is an antimuscarinic agent used as eye drops for refractive examinations. The aim of this study was to develop a simple and suitable analytical method for determination of tropicamide in eye drops in the presence of excipients. A zero-crossing third and fourth derivative spectrophotometric method was described for determination of tropicamide in eye drops. The measurements were carried outat wavelengths of 263.8 and 255.4 nm for third- and fourth-derivative, respectively. The method was found to be linear (r2&gt; 0.999) in the range of 10-100 µg/ml for tropicamide in the presence of excipients. The limit of determination was 10 mg/ml for tropicamide. The method was successfully applied for determination of tropicamide in eye drops without any interference from excipients or need to prior separation before analysis

Synthesis of 5,6-Diphenyl-2,3-dihydro-1,2,4-triazine-3-thione as a New Reagent for Spectrophotometric Determination of Palladium

Abstract: A new chromogenic reagent for the sensitive and selective determination of Pd 2+ ions in aqueous solution was synthesized. The reagent, 5,6-diphenyl-2,3-dihydro-1,2,4-triazine-3-thione, forms colored complexes with a few heavy metal ions. A 1:1 (M:L) yellowish orange colored complex of DPhDTT-Pd was formed in methanol. The molar absorptivity is 6.67×10 3 L mol -1 cm -1 . Bee&apos;s law was obeyed in the concentration range of 10-50 μg/mL at λ max 385 nm. The accuracy and precision of the method were evaluated on within-day and between-day basis; the relative error was ≤ 3.13 and the relative standard deviation was ≤3.96. The method was successfully applied to the synthetic samples and results compared with atomic absorption method. There was no significant difference between two methods (p&gt;0.05)